I was asked to do a tutorial on screenshots. I don't have the time or patience to upload a full-on tutorial, so you get a step-by-step instead. I'll go over a few of the steps here:
Sketch;; Simple process of sketching the character, basically just transitioning the image in my head to my digital sketchbook.
Lines;; ... Lines.
Flats;; No, I don't do the background before the flats. It's just the way I roll. And, as the word suggests, it's just flat colours. Shading comes after.
Eyes;; Abuse of the Pen Tool for the x'd-eye and Circle tool for the circle eye (I still can't draw straight lines or perfect circles). Outer Glow effect used.
Shading;; Following the light source (of which I forgot to show here -- I usually add arrows during the sketch phase). There are two layers, both with a clipping mask, set the Multiply, and with an Opacity set to 50%. Both layers also have a gradient, fading from a light blue-grey, to a dark blue-grey.
TIP: Never use a plain grey. It only makes the shadows look flat. Also, highlights are a good way to go, but for whatever reason, I decided to skip that phase.
Background - Sky;; A simple gradient from a blue to a lighter blue.
Background - Clouds;; A layer sitting above the background - sky. Used the brush tool for the clouds and the shading (of which are on the same layer). Slight abuse of the Motion Blur, but not much.
Background - Crosses;; Sloppily painted crosses with a black brush tool with the Opacity set at 50%. Also slight abuse of the Motion Blur.
Foreground - Wisps;; Same process as the crosses.
Black Bars;; Simple use of the Rectangle tool. Two layers merged to one.
Text;; Orange text with an Outer Glow effect. Blend mode set to Normal, Opacity to 100%, Spread set to 100, and Size set to 10.
Lastly, this is all done in PhotoShop CS4.